Twine knotters are mainly used in large mobile rectangular bale presses for straw, hay, silage and similar materials as well as in recycling applications, e.g. for bundling paper, textiles, thin metal sheets and the same. Binding or bundling devices, equipped with such twine knotters, can also be part of packaging plants for cording packets, bales or bundles of materials.
In stationary or large mobile bale presses, the pressing material is filled into a pressing channel, which is at least rectangular in cross-section, preferably pre-compressed and is pressed to a rectangular string of material. The material is partitioned into box-shaped bales, conventionally known as square bales. The upper and lower side as well as outer sides is encompassed in a longitudinal direction of the pressing channel with several twine threads. The threads are knotted before expelling the bale. The feeding of necessary twine, the knotting process within the twine knotter as well as the interaction of pressing elements involved in forming a double knot are described for common double knotters in DE 27 59 976 C1.
Depending on the width of the bale and its pressing density, two or more double knot twine knotters are mounted next to each other on the knotter drive shaft of a press. The selection of the twine knotter and the pressing elements, supporting the knotting process, are determined by the number of necessary strappings of a bale.
The knotter drive shaft is arranged above or below the pressing channel. Ordinarily, it is arranged at least approximately horizontal and in general parallel to the pressing channel. At other pressing channels, the drive shaft is arranged laterally.
The economic efficiency of the cereal stem harvest depends on the collecting, freight, and storage costs. Straw, especially shredded material, is used as bedding in poultry housing, dairy cattle cubicles and other stables. Straw further serves as feed in crude fibre weak feed rations as ground cover in strawberry cultivation and as a breeding ground for mushroom cultivation. To enable such applications, big bale presses are equipped with cutting devices or shredding devices at their front end. Generally in the feeding channel arranged in front of the main pressing channel, a pre-compressing of the pressing material is carried out. It is only transferred into the main pressing channel when a predetermined amount, with defined pressing material density, is available. Accordingly, high density bales with high weight are produced.
As the mobile presses are not only transferred from one to the other field but also are used extra farm wide, they have to be fit for over the road driving. Thus, they have to meet Road Traffic Licensing Regulations. This means that the machine dimensions are not increasable without limits. Also the dimensions of the individual bales have to have, for an optimal lorry loading and later storage, suitable measurements.
To increase the bale weight still further, wherein better transportation capacities can be utilized and the holding together of a bale is increased, an increase of the compression of the bale, with comparable moisture content of the pressing material, has to be accomplished. With such a goal in mind, consideration needs to be given to the currently available plastic pressing twines, mainly polypropylene twines, which have a limited tear strength. These twines will tear with increased pressing material density when the bale is expelled from the pressing channel. The thickness of the pressing twine, which is determined by the running length of the twine thread, is expressed in terms of how many meters of twine weigh one kilogram (units: m/kg). The twine thickness cannot be readily continuously increased. The individual knotter components are adjusted to the quality of the pressing twines. Thicker twines, with increased tear strength, would disadvantageously increase the dimensions of the twine knotter, wherein it is dubious whether a secure functioning of the twine knotter, especially according to the so-called Deering working principle, can be achieved.
In order to increase the weight of a bale at constant moisture content of the to be packaged material, without at the same time increasing the dimensions, WO 2011/054360 A1 proposes to increase the number of the to be knotted twine threads. Up to now, six twine knotters for knotting six parallel twine threads is common. The solution according to WO 2011/054360 A1 proposes eight twine threads. In this case, double knot twine knotters are provided, respectively, with one knotter drive disc non-rotationally mounted on the knotter drive shaft, driven around its axis and with a knotter chassis belonging to the knotter drive disc. The knotter chassis is spatially held stationary at one end relative to the pressing channel and at the other end relative to the knotter drive shaft. The knotter chassis carries one knotter assembly forming two knots one after the other. A knife lever is driven by a cam track of the knotter drive disc. The knotter assemblies comprise at least one twine holder, driven by a first drive tooth of the knotter drive disc. A knotter hook is driven by a second drive tooth of the knotter drive disc. The knife lever has a three-fold function. First, it serves as a twine guide. Second, it cuts the twine. Third, it pushes the twine loops off the knotter hook. The knotter assembly is arranged totally axially off-set relative to the hub of the knotter drive disc and of the drive-shaft sided end of the knotter chassis. The respective knotter assembly and, if necessary, also the pivot area of the knife lever overlap in an axis direction of the knotter drive shaft. The knotter drive disc of the neighboring double knot-twine knotter, over a partial length of the knotter assembly and, if necessary, also of the pivot lever of the knife area. In this manner, a certain de-coupling is achieved concerning the dimensional requirements of the hub of the knotter drive disc and those of the drive-shaft-sided attachment of the knotter chassis from the arrangement and construction of the knotter assembly and of the knife lever. Considerable length portions of the right and/or left neighboring double knot-twine knotter overlap with the double knot-twine knotter arranged therebetween. In this manner, the effective length of a double knot-twine knotter, in relation to the knotter drive shaft, can be shortened, as it is allowed by the drive assembly or the knotter assembly or the knife lever. The effective length of the double knot-twine knotter is determined by the assembly of the three assemblies, which, concerning the knotter drive shaft, has the largest length.
All above named twine knotters have the knotter drive discs, which are part of the twine knotter, arranged in sequence, one after the other, on the knotter drive shaft. If, due to a defect, one of the twine knotters has to be dismantled or exchanged, all knotter drive discs and, thus, all the twine knotters, which are arranged between the to be exchanged knotter drive disc and the end of the knotter drive shaft, also have to be dismantled.